This invention involves a novel process of making antimony trifluorodichloride and using it to fluorinate a fluorinatable hydrocarbon or halocarbon in one reaction vessel. Antimony trifluorodichloride is an extremely effective agent for the exchange of fluorine atoms for other halogen atoms on aliphatic hydrocarbons. See Henne, U.S. Pat. No. 1,978,840.
It is already known to prepare antimony trifluorodichloride by reacting antimony trifluoride and antimony pentachloride as disclosed by F. Swartz, Bull. Acad. Roy. Belg., 3 (24), p 474 (1892).
Daudt et al., in U.S. Pat. No. 2,005,705, disclosed the reaction of antimony pentachloride with hydrogen fluoride, and Dehnicke et al., Z. Anorg. Allgem. Chem., 323, 267-74 (1963) (CA 59:12300n), taught a process of reacting ClF.sub.3 and antimony pentafluoride in the presence of excess chlorine.
It is also known to prepare antimony trifluorodichloride from antimony trifluoride by contacting the solid reactant with gaseous chlorine in the absence of a liquid reaction medium. In this process, disclosed by A. Henne, Organic Reactions, 2, 49 (1944), solid antimony trifluoride is charged to a high pressure steel cylinder. The cylinder is then sealed, evacuated and chlorine in molar ratios of 5 to 100 percent of the antimony trifluoride is added. The cylinder must be heated and cooled for the antimony trifluorodichloride, a viscous liquid, to flow and expose fresh surfaces of antimony trifluoride. Occasional rolling of the cylinder helps to expose fresh surfaces of antimony trifluoride. The antimony trifluorodichloride from this process is extremely viscous and cannot be easily poured from the reaction flask. Further, due to the low available surface area at which chlorine may react with antimony trifluoride and the disparate phases of the two reactants, the reaction is extremely slow and not all of the antimony trifluoride is consumed even in the presence of excess chlorine.
In Henne, U.S. Pat. No. 1,984,480, antimony trifluoride was contacted with chlorine in the presence of either liquid antimony trichloride or antimony pentachloride, thereby producing a mixture of antimony trifluorodichloride and antimony pentachloride. As a fluorinating agent, the mixture thus produced is not as effective as antimony trifluorodichloride alone. A difficult to perform distillation of the binary mixture is therefore required in order to provide a suitably pure form of antimony trifluorodichloride.
It would be desirable to provide a method whereby antimony trifluorodichloride is prepared expeditiously, in high purity free of additional halogenated antimony compounds and in a manner easily adapted to further employ the antimony trifluorodichloride as a fluorinating agent.